Great advancements have been made in semiconductor technology in the last few years largely due to the discovery of new materials and the discovery of new methods of making better materials. These advances have led to new device applications for semiconducting materials and such applications often require different fabrication techniques. Typically, these techniques are aimed toward obtaining smaller size, more precise location of various geometrical features in the device, more accurate shapes for various geometrical features in the structure, greater adherence of metallic substances to the semiconductor surfaces, etc.
A particular case in point is the development of semiconductor devices involving indium phosphide and related compounds such as indium gallium arsenide phosphide and indium gallium arsenide. Typical devices are photodetectors, light-emitting diodes and semiconductor lasers. Generally, such devices operate at longer wavelengths than traditional III-V devices. Typical wavelengths for indium phosphide type devices are in the range from 0.8 microns to 2.0 microns, most particularly around 1.3 microns.
In fabricating such devices, it would be highly advantageous to have an etching procedure which can be controlled as to etch rate, area to be etched and geometrical shape to be etched. Such an etching procedure is usually referred to as an anisotropic etching procedure. Such a procedure would be useful for making channels, via holes, mirrors, lenses, diffraction gratings and in the separation of individual chips on a semiconductor wafer.
Photoetching has been carried out on n-type indium phosphide using ferric chloride solution (see D. Lubzens, Electronics Letters, 13, page 171 (1977)).